Some of the other candidates have spent massive amounts of money on campaign ads. The Right To Rise PAC which supports Jeb Bush for President has spent millions of dollars on ads. Many of them are attack ads against Donald Trump.
Trump's campaign has been very successful with the use of the media. The media is giving Trump the most coverage and its costing Trump nothing. According to Fox News the ad blitz that Trump wants to start will cost upwards to $2 millions a week. The ads will mostly focus on Trump's plan for America.